Linear-motor transducer



w. T. HARRIS 2,789,280

TJLEIJ. 9 l5 /0 INVENTOR MLBUR 7: l/flRQ/S ATTORNEYS Filed April 11, 1955 LINEAR-MOTOR TRANSDUCER 2 I I. WNW T l M 4 6 (m.

April 16, 1957 2,789,280 LINEAR-MOTOR TRANSDUCER Wilbur r. Harris, Southbury, .Conn., assignor to The Harris-Transducer Corporation, Wootlbury, Conn., a corporation of Connecticut s I 7 Application April 11, 1955, Serial No. 500,600

izclaims. .(cLsm-s Since the armature is fully enclosed, its motion is not I used for direct coupling to the medium except by reaction through a compliant connection to the stator, i. e. coupling to the medium by way of the stator.

It is an object of the invention to provide an improved device of the character indicated.

It is another object to provide a variable-position transducer structure in which all moving elements may be directly coupled to the medium in which the transducer is immersed, to produce an expander-type radiator, rather than a variable-position-type radiator, while still employing the variable-position-type mechanism.

It is a further object to provide an improved basic lamination configuration for a variable-position transducer and lending itself to provision in multiple (that is, to use in array configurations) in order to derive an extensive single radiating surface.

It is a further object to provide an improved variableposition transducer-driving mechanism for uniformly driving a diaphragm of extended area. a

It is a general object to meet the above objects with a structure requiring essentially no proportionally greater thickness (i. e. front-to-back, in the sense of longitudinal response normal to a transducer face or diaphragm) than for structures of said patent application, and for which copper requirements in an electromagnetically excited device can remain relatively small.

Also it is a general object to achieve the above objects with a structure requiring a minimum of strategic materials and having the power-handling capacity per-unit weight or per-unit volume of accepted industrial electrical equipment.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the artfrom a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, a preferred form of the invention:

Fig. l is a fragmentary horizontal sectional view through the top part of a laminated transducer incorporating features of the invention, certain parts being broken away or shown in section in order better to illustrate relationships; and

Fig. 2 is-a fragmentary sectional view substantially in the plane 2-2 of Fig. 1.

Briefly stated, my invention contemplates a modificamass areas.

Patented Apr. 16, 1957 tion of the variable-position transducer forms shown in said patent application. Such transducers lend themselves to magnetic excitation in such manner that, regardless of the amplitude of mechanical oscillation of armature and stator parts, the gap width between driving poles remains essentially constant. As distinguished from the forms of said patent application, my present invention contemplates that all reacting masses of the mechanically oscillatory structure shall be directly coupled to radiating faces, diaphragms, or pistons. Thus, basically, each transducer may comprise two diaphragms in back-to-back relation, each diaphragm directly supporting part of a motor, the motor parts being so arranged as to enable electromagnetic response for mechanical oscillations along the longitudinal axis (i. e. generally normal to the diaphragm faces).

In the form to be described, the transducer comprises a consolidated stack of like laminations of magnetic material, such as silicon steel. Each lamination consists essentially of two spaced end strips, which, on consolidation, form the two spaced back-to-back diaphragms. Inte grally associated with the first diaphragm, so as to define the first of the two reacting systems,.is a first plurality of mass areas in laterally spaced relation; these first mass areas are laterally interlaced with a corresponding plurality of mass areas of the second system, integrally including the other diaphragm. Longitudinally compliant connections, such as lateral strips, integrally connect adjacent mass areas of each system independently of the connection afforded by the diaphragm strips. The central parts of these connecting strips are longitudinally compliant, and the remaining mass areas are directly connected to said central parts in such manner that the mass areas of the two reacting forms react through the yieldable connections to oscillate with bodily displacement, in opposed-phase relation.

The stack of basic laminations can be excited directly, as by electro-magnetically driven reaction between adjacent mass areas of the two systems; alternatively, they may be excited parasitically, as by immersion in a liquid medium already excited by other means. Laminations may be formed integrally to comprise desired pluralities of adjacent pairs of reacting mass areas so that a single diaphragm may be elongated transversely of the response axis and may be served by a plurality of pairs of reacting Areas. of adjacent excited and parasitic stacks may be caused to resonate in unison, thereby extending the effective frontal area for a minimum employment of excited stacks.

'Referring to the drawings, my invention is shown in application to a basic radiator element comprising a consolidated vertical stack of like laminations 10 tied together by means of bolts 111213-14, and having a radiating response generally normal to the transducer end faces 1516 constituting the stacked longitudinal ends of laminations; throughout this description and in the claims, longitudinal is employed to connote the sense of bodily displacement in my transducer, i. e. normal to the end faces 15-16 at the particular transverse location under consideration. I

As in said copending application, the basic reacting mass areas 17--1817'-18', etc. are effectively independent, by virtue of the slot formations cut in the lamination 10. The radiating edges 15-16 are the limits of strips 1920, extending transversely of the longitudinal response axis for the desired transverse extent of the transducer. The strips are wide enough to be essentially non-yielding and to displace bodily upon application of thrust from the associated mass areas 1718. Laterally spaced mass areas 1717' are integrally and directly connected to one diaphragm 19, and laterally spaced mass areas 1818 are integrally and directly connected to the other diaphragm 20; when the laminations are consolidated into a stack, as suggested in Fig. 2, it will be understood that the sum total of the radiating edges 15 from the active outer face of diaphragm 19 and that edges 16 define diaphragm 20.

Also as in said patent application, stifily compliant means independent of the radiating faces are employed for reactive connection of the first system (comprising diaphragm 19 and mass areas 17-17) to the second system (comprising diaphragm 20 and the mass areas 1-8-18). Such compliant connection may be in the form of a laterally extending strip 21 connecting adjacent mass areas 17-17 of one system and a similar strip 22 connecting adjacent mass areas 18-18 of the other system. The most deflectable part of the com pliant connections 21-22 is the central portion, and to this central portion direct integral connection to the adjacent mass area is made, as indicated at 23 for connection of mass area 18 to compliant means 21.

As in said patent application, by forming the laminations of magnetic material, such as non-critical silicon steel, the construction lends itself to electromagnetic excitation. Such excitation may employ magnetic circuits with gaps of essentially constant width, and I have shown the provision of winding openings or slots defining first opposed poles or pole pieces, as at 24-25-24-25', for adjacent longitudinally extending edges of adjacent mass areas 13-17, along the elongated slot or gap 26. Similarly, slots along the gap 27 define second opposed poles or pole pieces, as at 28-29 and 28-29'.

The pairs of opposed pole pieces, as at 24-25 or at 28-29, are preferably not only transversely opposed, as shown, but also longitudinally oifset so that when the various flux paths are excited in unison, forces transverse to the structure are nullified and the only net forces generated are those of longitudinal relative propulsion of the mass areas 17-17 associated with one system, all with respect to the mass areas 18-18 associated with the other system. The pairs of pole pieces along the gaps 26-27 may be provided in any desired plurality, as dictated by design requirements, and in the form shown, the poles 24-45 represent one of a set of five pairs of poles along the gap 26, while the poles 28-29 represent part of a similardistribution of poles along the gap 27. Polarization and excitation windings may be coupled to these poles so as to establish relative flux polarities, as indicated by plus and minus symbols in the drawings. In the form shown, polarizing windings are contained in the slots between poles in the stator areas or mass areas 17-17, while excitation windings are contained in the slots between poles in the armature areas or mass areas 18-18. Thus, for any particular slot 26-27, the described windings develop forces in the direction in which the device is constrained to oscillate, namely, along the longitudinal axis. The oscillating mechanism has the characteristic of a linear, oscillatory, salient-pole, syn- Chronous motor. Winding connections can be, and preferably are, chosen for a balanced condition, so that two sets of D.-C. coils receive equal and opposite induced A.-C. voltages which balance out, making unnecessary the provision of series inductances in the D.-C. circuits, as will be understood.

In operation, that is, with the first system 19-17-17 in mechanical opposed-phase oscillation with the second system 20-18-18, the gap widths 26-27 do not change, regardless of the magnitude of mechanical oscillating excursions. This is true whether the device is excited parasitically or by way of the described electromagnetic means. Thus, all moving parts of the system are in one way or another directly coupled to radiating members 19 or 20, as the case may be.

As indicated generally above, the described unitary Variable-position motor, as represented by the mass areas 17-17 reacting with the mass areas 18-18, may complete the transducer, but for uniformity of longitudinal thrust development along a single elongated transducer or diaphragm face 15-16, I prefer to provide my basic lamination design in such eplural repetition as necessary for substantially uniformly distributed drive to the entire transducer face. Continuity of the lamination for this purpose is suggested by the broken lateral confines of the lamination in the drawing. The section line 2-2 designates a convenient cut-oft line determining a physical end of the transducer, and it will be understood that a similar cut-off will adequately determine the other end.

To complete the structure, the vertical -(i. e. in a sense perpendicular to the longitudinal and lateral senses) ends of the stack should be closed otf, as by end bells, but since the front and back edges 15-16 of these ends must freely resonate in opposed-phase relation, the end bells may not be rigid, but should yield with minimum resistance. For this purpose, I show in Fig. 2 the provision of an accordion-pleated .edge construction comprising two pleats 30-31, centrally secured as by welding, and secured at their outer limits to mounting flanges or angle members 32-33. The angle members 32-33-are attached respectively to their adjacent diaphragm ends, and, because there may .be .a small amount of deflection of the diaphragms in the spaces between securing bolts 13 (or 14, as the case may be I prefer to provide spacing washers 34 at locations of securing the angle members 32. The entire transducer may be sealed against moisture by encasing in a continuous rubber or neoprene boot 35.

Because the front and back diaphragms radiate in opposed-phase relation, I must mount the transducer so as not to interfere with free mechanical oscillation of these parts. In the form shown, I employ an elongated channel 36 overstanding the top and bottom surfaces of the transducer and at least coextensive with the transducer element. Of course, if more than one transducer element is employed in .an array, then the channel member 36 may be of such length as to span several similar transducer elements, all as described in greater detail in my copending application Serial No. 493,796, filed March 1], 1955. In order yieldably to connect a frame member 36 to the described transducer, I have shown provision of elongate-d rubber or rubber-like strips 37-38 at least coextensive with the transverse extent of the transducer and anchored by bolt means 33 to the frame, 36 and by bolt means 39 to the angle member 32 .of the transducer. To improve the strength of support thus provided, I indicate my preference for metal reinforcements 40-41 bonded integrally to the connecting strip 37, at least at locations of bolts 38-39, all as described in greater detail in my said copending application Serial No. 493,796, now Patent No. 2,756,405, and in my copen'cling application Serial No. 454,712, filed September 8, 1954. To integrate the frame member '36 with further frame structure, securing holes maybe provided at 41-42 as needed.

As indicated generally above, my basic resonant structure lends itself not only to the internally driven embodiment presently described in detail, but also to parasitic or external excitation. For such purposes, the windings described may be omitted or may be merely not excited. However, for lower cost, I prefer a simpler lamination construction which provides simply elongated slots 26-27, uninterrupted by winding slots, as will be understood. By proportioning the parts of such a parasitic transducer in the manner analogous to the parts of Fig. 1., the parasite may have the same inherent mechanical resonant properties as a driven transducer and may be employed in side-by-5ide relation therewith, all as described in greater detail in my said application Serial No. 481,988.

It will be seen that I have described an ingenious variable-position transducer lending itself to :efl'icient, high-power .electroacoustic conversion at very low frequencies. Regardless of the amplitude of mechanical oscillation, there is no appreciable change in gap width,

and large, forces can be established between the reacting oscillating masses. With proper core and coil design, efficiencies of the order of 90 percent may be achieved at frequencies as low as 30 C. P. S. The basic front-toback symmetry of my device establishes a matching of reacting oscillating masses, thus determining a highly efficient mechanical resonator.

While I have described the invention in detail for the preferred form illustrated, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

1. A mechanically resonant combination, comprising two diaphragms in spaced back-to-back relation, 2. first plurality of masses connected directly to one of said diaphragms on the side facing said other diaphragm and in laterally spaced relation, a second plurality of masses connected directly to said other diaphragm on the side facing said one diaphragm and in laterally spaced relation, the masses of said pluralities being laterally interlaced, whereby a first system comprising one diaphragm and associated masses is interlaced with a second system comprising the other diaphragm and associated masses, and means ocmpliantly interconnecting said system for opposed-phase oscillation on an axis generally normal to said diaphragms.

2. A mechanically resonant combination, comprising a consolidated stack of like laminations defining two diaphragms in spaced back-to-back relation, a first plurality of masses directly longitudinally connected to one of said diaphragms on the side facing said other diaphragm and in laterally spaced relation, a second plurality of masses directly and longitudinally connected to said other diaphragm on the side facing said one diaphragm and in laterally spaced relation, the masses of said pluralities being laterally interlaced, whereby a first system comprising one diaphragm and associated masses is interlaced with a second system comprising the other diaphragm and associated masses, and means integrally associated with each system and compliantly interconnecting said systems for opposed-phase oscillation on a longitudinal axis generally normal to said diaphragms.

3. A transducer lamination having longitudinally spaced opposed substantially parallel radiating edges, said lamination being internally slotted with a plurality of slot configurations determining spaced laterally extending diaphragm portions at said radiating edges and in back-to-back relation, a first plurality of mass areas integrally connected directly to one of said diaphragm portions on the side facing said other diaphragm portion and in laterally spaced relation, a second plurality of mass areas connected integrally .and directly to said other diaphragm portion on the side facing said one diaphragm portion and in laterally spaced relation, the mass areas of said pluralities being laterally interlaced, whereby said lamination may be said to consist of a first system comprising one diaphragm portion and associated mass areas interlaced with a second system comprising the other diaphragm portion and associated mass areas, and means integrally connecting said systems with longitudinal compliance for opposed-phase oscillation along an axis generally normal to said diaphragm portions.

4. A lamination according to claim 3, in which said lamination is of magnetic material, and in which adjacent edges of the masses of said interlaced systems are slotted to define laterally opposed pole pieces on adjacent parts of adjacent mass areas.

5. In a transducer of the character indicated, two diaphragms in spaced back-to-back relation, a first plurality of masses connected directly to one of said diaphragms on the side facing said other diaphragm and in laterally spaced relation, a second plurality of masses connected directly to said other diaphragm on the side facing said one diaphragm and in laterally spaced relation, the masses of said pluralities being laterally interlaced,

whereby a firstsystcm comprising one diaphragm and associated masses is interlaced with a second system comprising the other diaphragm and associated masses, and means electromagnetically reacting between said systems and driving said systems in longitudinal oscillation on an axis substantially normal to said diaphragms.

6. In a transducer for liquid immersion, two diaphragms in spaced back-to-back relation, a first plurality of masses connected directly to one of said diaphragms on the side facing said other diaphragm and in laterally spaced relation, a second plurality of masses connected directly to said other diaphragm on the side facing said one diaphragm and in laterally spaced relation, the masses of said pluralities being laterally interlaced, whereby a first system comprising one diaphragm and associated masses is interlaced with a second system comprising the other diaphragm and associated masses, means compliantly interconnecting said systems for opposed-phase oscillation on a longitudinal axis generally normal to said diaphragms, and means electromagnetically reacting between said systems and against the action of said compliant interconnection for electroacoustic coupling to the liquid medium.

7. A transducer according to claim 6, in which adjacent interlaced masses of said respective systems are respective'ly armature and stator parts of motor means constituting said electromagnetic means.

8. In a transducer of the character indicated, a consolidated stack of like laminations, each lamination comprising spaced elongated edge strips which, when said laminations are consolidated, serve to define two diaphragms in spaced back-to-back relation, a first plurality of mass areas connected directly and integrally to one of said diaphragms on the side facing said other diaphragm and in laterally spaced relation, a second plurality of mass areas connected integrally and directly to said other diaphragm on the side facing said one diaphragm and in laterally spaced relation, the masses of said pluralities being laterally interlaced with adjacent edges defining straight slots extending parallel to a longitudinal response axis generally normal to said diaphragms, the opposed adjacent lateral edges of the mass areas defining said slots having formed therein a plurality of winding pockets defining therebetween longitudinally staggered pole pieces, and winding means in said pockets and coupled to the poles defined between pockets.

9. A transducer according to claim 8, in which the number of pairs of opposed pole faces along each slot between adjacent mass areas is the same.

10. A transducer according to claim 9, in which balanced excitation windings are coupled to the poles of one of the mass areas along a given slot and balanced polarizing windings are coupled to the poles on the other mass area alongside said given slot.

11. In a transducer of the character indicated, an elongated substantially flat diaphragm, a plurality of armature elements connected in direct longitudinally thrusting relation with said diaphragm, a second diaphragm in backto-back relation with said first diaphragm and carrying a plurality of stator elements in direct longitudinally thrusting relation therewith, each said stator element being in magnetically coupled relation with a corresponding armature element for electromagnetic response along a longitudinal axis generally normal to said diaphragms, and longitudinally compliant means interconnecting said diaphragms and yieldably reacting against said electromagnetic reponse.

12. In a transducer of the character indicated, a consolidated stack of like laminations, each lamination comprising two strips in parallel spaced relation and defining on consolidation a pair of spaced diaphragms in back-toback relation, a first plurality of laterally spaced mass areas integrally and directly connected to one of said diaphragms in the space between said diaphragms, a second plurality of laterally spaced mass areas laterally inter laced with said first mass areas and integrally and di- Tectly connected to the other of said diaphragms, laterally extending means intergra'l with each "lamination and connecting each two adjacent masses of one of said pluralities, such connection being independent of the connection adjacent both diaphragm strips and defining cen- No references cited. 

